The decision to block access marks an apparent break from rules previously established by Romney's campaign.

Reporters usually are allowed to cover President Barack Obama's fundraisers held in public venues.

A Romney aide who was not authorized to speak for the record said the event is closed to the media because it is a "finance meeting" instead of a fundraiser. The aide said fewer than 40 people will attend, which is usually the threshold for access.

Ryan attended two Denver-area fundraisers on Monday night where media coverage also was prohibited.